1. Technical Field
The apparatus and methods disclosed, illustrated, and claimed in this document pertain generally to internal combustion engines. More particularly, the new and useful parallel cycle internal combustion engine pertains to an engine having two opposed cylinder blocks each containing four dual-chambered cylinders arranged in two-by-two cloverleaf fashion. The four dual-chambered cylinders employ four working members, including (i) double-headed and double-sided pistons in (ii) dual-chambered cylinders. The double-headed and double-sided pistons in dual-chambered cylinders cooperate with (a) a unique linear throw crank mechanism, (b) a multipurpose and multifunctional rotatable disk valve, (c) an integrated internal compressor, and (d) a multi-fuel combustion subsystem that, in combination, provide an engine capable of delivering fuel efficient, nontoxic, nonpolluting, inexpensive, safe vehicular travel without sacrificing power, environmental concerns, or load capacities. While the parallel cycle internal combustion engine can be manufactured in a wide range of sizes, a dynamic operating range is achievable with a smaller, lighter engine than has been customary.
2. Technical Background
Environmental pollution, global warming, and an almost exclusive reliance on petroleum to fuel commerce and vehicles conspire to jeopardize the stability of many nations. The need for significant energy alternatives is axiomatic. Equally evident is the need for dramatic improvement in efficient utilization of existing resources as the cost of petroleum continues to escalate. The apparatus described, illustrated, and claimed in this document is responsive to overcoming many direct and indirect problems presented by those challenges.
Conventional four-stroke engines function by implementing a series of discrete, discontinuous, rigidly linked, thermodynamic events. Conventional engines sequentially perform the well-known thermodynamic events of compression, combustion and power. Each event is conducted in a common location. In contrast, the parallel cycle internal combustion engine disclosed hereby performs the thermodynamic processes continuously in distinct, separate locations. Thus, for example, while conventional engines cannot capture, store or use surplus energy generated during operation of an engine, the apparatus of this document does.
In general, a conventional four-stroke engine alternates between functioning substantially as an air compressor and a heat-enhanced compressed air motor. Each phase of the four-stroke cycle must be completed within a defined time interval that is completely predicated on engine speed. Each cycle is also interdependent, meaning that each event results from a predecessor event. For example, power is generated only if a preceding compression created a charge necessary for combustion; compression results only if sufficient power is generated by a previous expansion. Individual thermodynamic events also are subject to synergistic restrictions. Ultimate capabilities of most engines are limited by a specific compression ratio defined during engine design by the bore and stroke.
The conventional four-stroke thermodynamic process results in several limitations. As indicated, all thermodynamic events must occur within a common space location. Excess energy, in the form of heat and pressure, produced during operation of an engine must be eliminated from a cylinder before the next intake stroke begins, and is unavailable for direct regenerative processes. Conventional engines also require a minimum idling RPM (“revolutions per minute”) and an auxiliary energy storage mechanism, like a flywheel, to continue a cycle when there is no power stroke.
Conventional engine designs are approaching the limit of their capabilities. Recent innovations involve hybrid concepts that are not specifically improvements of the engine per se. Hybrid concepts address some limitations of conventional four-stroke engines; regenerative braking appears to be the major advantage of the so-called “hybrids.” Reversing an electric motor allows a generator, when loaded, to decelerate a vehicle. Regrettably, however, a hybrid vehicle also requires addition of a separate energy system to achieve regenerative braking, not required by the parallel cycle internal combustion engine.
Environmental and efficiency concerns have stimulated decades of incremental engine refinements. Yet current engine design and manufacture remain based on principles identified more than a century ago. Innovative alternatives in structure and function have failed to demonstrate compelling advantages; none has displaced traditional Otto and Diesel cycle engines except in certain specific domains, such as turbine jet engines. Although alternatives, such as the hydrogen fuel cell, are widely investigated as eventual solutions, the weight of electric motor/fuel cell devices remains problematic. Until fuel cell applications develop a power density sufficient to fly a helicopter, for example, the need for internal combustion engines will persist.
However, environmental deterioration and depletion of oil reserves ultimately will limit use of internal combustion engines. The only question is whether viable alternatives can be deployed before social, environmental, and/or economic problems preclude an orderly transition. A new engine design that offers enhanced performance, with both reduced emissions and fuel consumption, would be a highly desirable component of such an orderly transition.
The presently disclosed parallel cycle internal combustion engine promises significant improvements in overall efficiency, enhanced dynamic performance, and decreased environmental emissions. The engine is scalable, versatile, and easily integrates with existing structural components. Some advantages of the apparatus disclosed, illustrated and claimed in this document are the result of innovation in three areas, (i) thermodynamic concepts, (ii) mechanical and operational processes, and (iii) engine and vehicle design.
The thermodynamic concepts implemented in the parallel cycle internal combustion engine represent a fundamental departure from conventional two- and four-stroke cycles. A variety of distinctive mechanical and operational processes are disclosed that amplify advantages inherent in the proposed thermodynamic concepts. A compact and dynamic engine design emerges from a unique association of these thermodynamic, mechanical, and operational innovations. The resulting engine provides opportunities for a paradigm shift in vehicular design with important environmental and economic advantages.
An understanding of the concepts associated with conventional engine design will enable an appreciation of the parallel cycle internal combustion engine. The defining distinction between parallel cycle engines earlier disclosed, also known as Brayton or split-cycle engines, and conventional four-stroke engines, also known as Otto and Diesel engines, is the physical rather than temporal separation of compression and expansion functions. Separation of compression and expansion functions was disclosed more than a century ago in, for example, U.S. Pat. No. 125,166 to Brayton in 1872. In Otto and Diesel cycle engines, a single working chamber alternately performs compression and expansion processes in series. In Brayton cycle engines, different working chambers simultaneously perform compression and expansion functions in parallel. Although a number of potential advantages are associated with the Brayton cycle concept, the need for separate compression chambers, in part, has inhibited development of a successful Brayton cycle engine.
Therefore, an engine in which a single working chamber simultaneously performs distinct compression and expansion functions in parallel would be advantageous. However, although Brayton cycle concepts are successfully applied in conventional turbine engines, a successful reciprocating piston embodiment has not displaced the familiar Otto and Diesel engines.
Environmental and economic concerns related to petroleum once again suggest exploration of the advantages inherent in a split-cycle engine as disclosed in this document. Advantages include increased efficiency through variable compression and expansion ratios; heat regeneration; complete combustion of an array of different fuels; simplified, compact design; and options for regenerative braking. New and novel features, and new and novel combinations and improvements of existing characteristics of split-cycle engines, may be exploited to achieve those benefits, including separate combustion chambers, compressed air accumulators, rectilinear connecting rod motion, double-headed double-sided working member pistons, motive fluid conditioning, rotating disk valves, and structurally integrated but functionally independent compressors.
As acknowledged by those skilled in the art, a significant feature of parallel cycle engines is separation of compression and expansion chambers. Two fundamental characteristics distinguish the capabilities of previously disclosed parallel cycle engine: (1) what happens to the compressed air as it travels between compression and expansion chambers; and (2) the nature of the driving forces between the compression and expansion chambers.
Those of skill in the art will recognize that a significant feature of the parallel cycle engine disclosed herein is the capability to store additional energy as compressed air. Additional compressed air may be acquired from a number of sources, such as regenerative braking, which converts vehicular kinetic energy into potential energy of compressed air using an engine's compressor function. These advantageous features require at least the capability of retaining an excess supply of compressed air.
Separation, in space and time, of compression and expansion events allows modification and conditioning of compressed air. A diabatic compression, i.e., compression without gain or loss of heat, is associated with higher temperatures and pressures than isothermal processes with the same compression ratio. In attempts to decrease both temperature and pressure, while increasing the mass of oxygen within a given volume, some references appear to suggest decreasing compressed air temperature by removing heat.
Relocation or removal of the combustion process from an expansion cylinder offers numerous advantages. Power output is then a function of the rate at which compressed air may be supplied to the combustion chamber, not the mass of oxygen available at the end of the compression stroke. A separate combustion chamber also reduces constraints on fuel characteristics by allowing extended time for fuel combustion, such as continuous combustion, rather than the brief time allowed during conventional Otto and Diesel cycles. Continuous combustion also enhances the possibility of a complete burn of fuel with sufficient oxygen to minimize particulate and carbon monoxide emissions. In addition, a separate combustion chamber provides the freedom to arbitrarily adjust air/fuel mixtures. Although a separate combustion chamber may be constructed of heat-resistant materials, such as ceramics, the same materials have been difficult to incorporate into conventional Otto and Diesel engines.
Continuous combustion also offers an opportunity to modify, enhance or condition the motive fluid in a split-cycle application, but this has proven difficult when combustion is limited to the brief time limits inherent in the design of conventional Otto and Diesel cycles. As taught in this document, motive fluid temperature can be reduced by utilizing a portion of its internal energy to provide the water's latent heat of vaporization.
In one aspect of the parallel cycle internal combustion engine disclosed and claimed in this document, water injection is used and applied. Unlike temperature reduction with heat rejection through an intercooler, water injection lowers the temperature through a heat regeneration process that produces additional active motive fluid molecules in the form of steam. Reduction of temperature also reduces noxious emissions.
In the disclosed engine, the motive fluid that enters an expander has the same chemical composition as the expanded fluid that exits the expander. This presents important opportunities for simplification of valve functions. A person skilled in the art will appreciate that rotary valves may have several advantages over conventional poppet valves. The advantages include volumetric efficiencies, elimination of reciprocating motion, and decreased mechanical and functional complexity.
Accordingly, the variable-aperture, symmetric, dual-function, multi-cylinder valve for a parallel cycle engine as disclosed and claimed in this document would be advantageous. The rotary disk valve disclosed in this application includes a variable-aperture, symmetric, dual-function valve that serves four parallel expansion cylinders disposed in a two-by-two cloverleaf arrangement.
As a person skilled in the art will appreciate, there are drawbacks to the use of conventional eccentric crank mechanisms that seek to convert linear motion of the piston to rotary motion of the crankshaft. Some problems with conventional cranks are (1) inefficient conversion of cylinder pressure into crankshaft torque; (2) large lateral forces on the piston; (3) engine vibration; and (4) the inability to form a tightly sealed cylinder base. Prior art has suggested solutions that include offset crankshafts, swash plates, and planetary gear arrangements. Other references allude to particular planetary gears to obtain strict rectilinear motion of the connecting rod, some of which suggest sealing the base of the cylinder and a double-sided piston function. Double-headed pistons are advantageous because of the possibilities of direct force transfer, dissipation of lateral cylinder forces, and the opportunity for compact, directly opposed-cylinder engine design.
However, the unique arrangement of planetary gears disclosed, illustrated, and claimed in this document produces strict linear motion of a crank pin. Strict linear motion of the crank pin has five primary advantages. First, lateral forces on the piston are virtually eliminated. Second, the base of the cylinder can be sealed, allowing double-sided piston action. Third, two pistons can be rigidly integrated as a single structure. Fourth, improved leverage increases torque capture. And, finally, engine vibration is significantly reduced.
A major advantage of this arrangement is the ability to simultaneously employ both sides of each of the two integrated pistons. Although separation of expansion and compression functions is presumed in connection with parallel cycle engines, structural separation is not required if functional separation can be achieved-in a novel fashion. In the parallel cycle internal combustion engine disclosed and claimed in this document, linear motion of the connecting rods allow tight closure of the cylinder base, while allowing the upper portion of a single cylinder to function as the expander, and the lower portion to simultaneously function as the compressor. Prior art has not disclosed these advantages.
The present invention discloses and claims a powerful, compact engine that incorporates new and novel structures, and cooperation of structural components that includes: (1) independently variable expansion and compression ratios; (2) multi-cylinder, variable aperture, symmetrical disk valves; (3) strict rectilinear connecting rod motion; (4) rigid, one-piece working members that consist of double-headed, double-sided pistons; (5) separate combustion chambers; (6) compressed air accumulator with regenerative braking capabilities; and (7) capability for motive fluid conditioning of water, peroxide, or alcohol injection.
Because of the limitations of a conventional four-cycle internal combustion engine, a need exists in the industry for a new, useful parallel cycle internal combustion engine capable of providing a compact, light, mechanically simple engine that yields improved performance while increasing fuel efficiencies and decreasing emissions.